Current emission control regulations necessitate the reduction of pollutant species in diesel engine exhaust. NOx, principally NO and NO2, contributes to smog, ground level ozone formation and acid rain. NO is produced in large quantities at the high combustion temperatures associated with diesel engines. NO2 is formed principally by the post oxidation of NO in the diesel exhaust stream. Exhaust after treatment devices achieve NOx reduction by using a reductant agent. The reductant agent is added to the exhaust gas entering the after treatment device and reacts with NOx over a catalyst in a process of selective catalytic reduction (SCR). Typical reducing agents may include light hydrocarbons and oxygen bearing compounds like alcohols.
Known methods of supplying the reductants may involve supplying the reducing agents and the fuel separately or may involve chemically producing the reducing agent in situ from the fuel itself. Such methods typically employ complex subsystems such as special purpose pumps, filters, storage tanks and the like. Additionally, these systems also require valuable space and specialized materials, thereby involving additional expenses. Accordingly, there is need for an improved system and method for supplying reductants to provide better overall economy and ease of operation.